A Converged Cable Access Platform (CCAP) is an industry standard platform for transmitting video data and voice content. CCAP is led by CableLabs® of Sunnyvale, Calif. CCAP unifies the Converged Multiservice Access Platform (CMAP), managed by Comcast Corporation of Philadelphia, Pa., with the Converged Edge Services Access Router platform (CESAR), which is managed by Time Warner Cable, Inc. of New York, N.Y.
A virtual Converged Cable Access Platform (CCAP) is software that performs the functions of a hardware-based CCAP. The virtual CCAP may execute on hardware components that include a commercial off-the-shelf switch/router and one or more off-the-shelf computing servers. A commercial example of a virtual CCAP is CableOS™, available from Harmonic, Inc. of San Jose, Calif.
CableLabs has publicly issued a Remote PHY family of specifications known as the MHAv2 specifications (Modular Headend Architecture version 2). These specifications describe how a CCAP platform may be separated into two components, (1) a CCAP Core located at a cable headend, and (2) a Remote PHY node (RPN), which is typically located outdoors.
The CCAP Core may transmit multiple downstream channels to a plurality of RPNs. Each RPN, in turn, may transmit those downstream channels to a plurality of cable modems. A cable modem will typically have less channel capacity than the CCAP Core. For example, a particular cable modem may be able to receive eight downstream channels, but the CCAP Core might be able to transmit on 24 or 32 downstream channels. Because of this, the CCAP Core may arrange the number of downstream channels it supports into groups and subsequently deliver a group of downstream channels to cable modems based on some arrangement.
To illustrate, the CCAP Core may divide a set of 24 downstream channels into three groups of eight channels, four groups of six channels, or six groups of four channels, for example. The CCAP Core may then deliver three groups of eight downstream channels to three different sets of cable modems capable of receiving eight downstream channels. Alternately, the CCAP Core may arrange those 24 downstream channels into six groups of four downstream channels; a cable modem capable of receiving eight downstream channels could receive, from the CCAP Core, four downstream channels that are shared with another set of cable modems and four downstream channels that are not shared with another set of cable modems. Thus, the CCAP Core may perform load balancing of a kind by adjusting how downstream channels are organized into groups and how those groups of downstream channels are delivered downstream to cable modems.
CableLabs has also issued a technical report about the R-MACPHY architecture and is currently undertaking an effort to formalize a specification for R-MACPHY products, specifically a Remote MACPHY Device (RMD) which resides in a Remote MACPHY node (RMN). This technical report describes Remote MACPHY (or MAC-PHY) as a generic term given to the distributed CMTS/CCAP architecture where the DOCSIS MAC and PHY layer processing of a CMTS are moved from the headend down to a Fiber Node location.